VIABILITY OF THE TYPHOID BACILLUS IN SEWAGE. 129 



a sample for purposes of control, it was connected with an aerating 

 apparatus which furnished between 100 and 150 bubbles of air per 

 minute from a tube of five mm. calibre. The material was exposed to 

 diffuse sunlight at room temperature. Samples were taken every two 

 hours for fourteen hours, then later after twenty-five, twenty-seven, and 

 thirty-three hours had elapsed. The conditions of the experiment were 

 made to conform as nearly as possible with the premises advanced by 

 the builders of the Chicago drainage canal in the construction of that 

 project. These, in brief, are that the sewage diluted twenty times its 

 volume with lake water will purify itself in a flow of twenty miles in a 

 current of about one and a half miles per hour. 



Experiment IV. A liter of the experimental sewage, undiluted was 

 aerated in a similar manner and samples taken after the same inter- 

 vals of time as in the previous experiment. The purpose of this was to 

 serve as a control, and to learn the effects of the aeration alone. 



Experiment V. Five hundred c.c. of the experimental sewage was 

 placed in a sterile flask and exposed to diffuse sunlight. This was exam- 

 ined for some time at intervals of two or four days, to ascertain the effect 

 of sunlight. 



The object in each of the foregoing experiments, as before stated, was 

 to learn the effects of the conditions described on the typhoid bacillus 

 more definitely to ascertain if such conditions caused or contributed to 

 the total disappearance or destruction of the organism of typhoid fever. 

 Hence the most expedient and practicable method of isolating the ty- 

 phoid bacillus was employed. 



Method. In each instance, a beef-tea tube was inoculated with one c.c. 

 of the sewage, and this after twenty-four hours' incubation was plated 

 in litmus lactose agar. As is commonly known, the typhoid germ does 

 not produce acid, while the colon organism from which it is to be dif- 

 ferentiated chiefly, is a marked acid producer. The typhoid colonies 

 which develop on this media do not alter the blue litmus but appear as 

 gray or white spots, whereas the colon colonies stand out distinctly 

 bright red in color. Advantage is taken of this, and isolations were 

 made onlv from the non-acid colonies, directlv into gelatin tubes. From 

 eight to twenty gelatin stabs w.ere made from each set of plates. These 

 tubes we];e permitted to develop, at room temperature for from four to 

 six days, when such as showed liquefaction were discarded since the 

 typhoid organism is a non-liquefying one. The indol test was then made, 

 and those cultures giving this reaction were also thrown out since the 

 typhoid bacillus is not an indol producer. Litmus milk cultures, potato 

 streaks and fermentation test were then made and such as exhibited 

 characteristics apart from those of the typhoid germ were likewise 

 discarded. The morphology was then studied, beef-tea cultures being 

 employed for this purpose. The agglutination tests are not yet 

 complete. 



Summary of Results of Experiments. Sufficient time has not 

 elapsed since the institution of this study for its completion, therefore 

 one cannot speak positively of the results. The cultural work, however, 

 offers some interesting indications, and these are as follows : 



Experiment I. The bacterial flora of sewage. This study is not as 

 yet complete, and consequently the organisms have not been classified. 

 17 



